This invention relates to a control system of an injection molding machine, and more particularly to a control system of an injection molding machine wherein an operator can directly observe various parameters of the molding condition, can correct the parameters, can set them from outside and can display them.
FIG. 1 is a block diagram showing the steps of one molding cycle of a plastic injection molding machine. On the upper row of FIG. 1 are shown the steps of injection and plastic filling, pressure holding, and metering effected by the injection molding machine, while the lower row shows the steps of mold clamping, mold cooling, mold opening and product taking out executed on the side of a metal mold.
When molding various products with an injection molding machine, as shown in FIG. 1, the molding conditions of the products are influenced by a number of physical parameters such as temperature, pressure, speed or position and the type of resin at respective steps, so that in order to obtain satisfactory products it is necessary to correctly determine the values of many discrete parameters. For this reason, it has been necessary to determine the molding conditions necessary to obtain satisfactory products by using past experience as well as results of repeated tests.
In order to determine best molding conditions in the prior art, digital switches corresponding to such parameters as the temperature, pressure, speed, position, etc. regarding the molding conditions were mounted on a control panel having graphically depicted setters for respective parameters and display devices. With this construction, the operator corrects the values of respective digital switches according to the result of cut and try tests. With such a prior art method, however, the operator must manually correct the data regarding the parameters, so that in a system utilizing digital switches, settings and displays are done simultaneously by the operator. Such a method does not cause any serious problem where fixed data are set and displayed, but it is impossible to directly display (load performance) molding data rear out from a external memory medium on the operating panel without relying upon correction operations of respective switches performed by the operator.
Thus using a method wherein molding data for satisfactory products are obtained by a series of cut and try tests, and where the data of the digital switches on the operating panel are corrected, the contents and settings of the digital switches before correction by the operator are lost. Thus, it is necessary for the operator to record the contents of the digital switches each time a test is made.
Lack of storing performance regarding the molding data prolongs and complicates the process of the cut and try method wherein various parameters are corrected from time to time, products corresponding to the corrected parameters are molded and the parameters are corrected by observing correlations between various molding data and molded products.
In recent years, instead of using an operating panel provided with digital switches, a system utilizing a cathode ray tube (CRT) display device has been used. This system, however, is not only expensive, but also the screen of the CRT can display only divided pictures formed by dividing the operating panel into a number of sections. Moreover, when setting or correcting values of respective divided sections with operating keys, it is necessary to move a cursor to a portion, and then input data with a key. Accordingly, where there is much data to be corrected or set, since it is necessary to select a divided section, to move the cursor and to input data with keys, the operator can not immediately correct and set the molding data.
Where a write pen is used for the CRT display device, it is not necessary to use a key for inputting data to move the cursor, but such system is also expensive and must use divided sections and data input keys.
For simplifying the operation, it is advantageous to install the CRT display device near the injection molding machine together with the operating panel, but where the CRT is installed near the molding machine, it will be destroyed by vibrations or shocks as well as high temperatures.